Dryer Transition Ducts, Lint, and Fires safety alert.

Reblogger David Popoff
Real Estate Broker/Owner with DMK Real Estate Ct RE Broker 0789963

Along with changing batteries in your smoke detectors cleaning your dryer annually is something all homeowners, landlords and tenants should do. This is a safety issue but also will let your dryer work more efficiently and last longer.


Original content by Reuben Saltzman

Last week I blogged about clothes dryer ducts, and this week I'm going to follow up with information on dryer transition ducts.  As I mentioned last week, a dryer transition duct is the flexible material that can be used to transition between the dryer and the duct.  Transition ducts should be used sparingly, stretched tight, not smashed, and replaced periodically.    They're allowed by the Minnesota State Mechanical Code, but they can't be any longer than 8', and they need to be listed and labeled for the application.  The key word is listed.   If a dryer transition duct is listed, you'll find the "UL" logo somewhere on the package or product.

Today I'll discuss the three most common materials used for dryer transition ducts, and I'll cover some basic rules for keeping your dryer transition duct safe.

Plastic Ducts

Plastic dryer transition ducts are a potential fire hazard.  They're never UL listed, they can get clogged with lint, and they'll burn.  If you have one of these, replace it.  I looked for one of these at Home Depot and Menards, but I couldn't find one.  Good.  I still find plenty of them while inspecting houses though.

Clogged Dryer Duct

I tried lighting some paper on fire inside one of these plastic ducts to see how fast it would burn through, and the plastic itself actually caught on fire.


Foil Ducts

Foil dryer transition ducts are typically UL Listed, and they're readily available at any home improvement store.  While these products are allowed by code, I've heard that many municipal inspectors won't allow them, and most manufacturers of clothes dryers don't recommend them either.

Foil Duct

I tried burning one of the UL Listed foil ducts by filling it up with shredded paper, then lighting the paper.  Once the paper caught fire, I accelerated the burn by aiming the blower end of a wet/dry vac at the tube.  Some people claim that these foil ducts are flammable, but that's not true; there are two versions of the foil dryer transition ducts - a listed and a non-listed version.  That's the listed version shown in the photo below.  After heavy white smoke started pouring out the end, it took about 10 seconds for the flames to rip through the side.

UL Listed Foil Duct

Semi-Rigid Metal Ducts

Semi-rigid metal dryer transition ducts are available anywhere dryer duct materials are sold, but it's almost impossible to find a UL Listed version of this.  The strange thing is that these semi-rigid ducts seem to be universally accepted by building code officials, and they're recommended by clothes dryer manufacturers.  Everyone seems to like these, but they have their drawbacks: they puncture easily, they crush easily, they unravel easily, and they have very sharp edges.  I repeat, very sharp edges.

After a ton of searching at local retailers and searching online, I couldn't find a single UL Listed semi-rigid duct, so I concluded there was no such thing as a UL Listed semi-rigid metal duct.

But there is.

I sent out emails to several major clothes dryer manufacturers, asking what consumers are supposed to use for a dryer transition duct, because there doesn't seem to be a UL listed semi-rigid duct.  Finally, a very helpful person at Whirlpool by the name of Lee Herendeen sent me a link to just such a product, made by Lambro Industries, Inc.  After all the searching I had been doing, I was skeptical that this was the real thing, so I ordered one.  It's the real thing.

The photo below shows the UL listed semi-rigid duct from Lambro sitting next to a non-listed duct.

Listed vs non-listed duct

The UL listed duct was much stiffer than the non-listed duct, and was much more difficult to crush.   To continue my comparison of transition ducts, I stuffed them both full of shredded paper, lit the paper on fire, then aimed the exhaust from a wet/dry vac in to the duct to simulate the air from a clothes dryer.

I started with the non-listed duct.

At about the 40 second mark, heavy smoke started to come out the back side of the duct.  About 17 seconds later the fire burned through the duct.

The next test was to try the same thing with the UL Listed duct.

With this one, heavy smoke started coming out at about the 30 second mark, and it took about 27 seconds for the fire to burn through the duct.  Of course these aren't 'real life' tests of a dryer duct fire, but it's interesting to compare the performance of the different materials.


Don't use plastic for your dryer duct.  It's flammable.

Foil comes in a UL Listed flavor and is easy to work with, but it's prohibited by many building code officials and clothes dryer manufacturers.

Semi-rigid aluminum is good, but it's a hassle to work with.  If you're going to use semi-rigid, use the UL listed version.

Next year I might check out a product called DryerFlex.  They claim their product offers the best of both worlds.  We'll see.

Reuben Saltzman, Structure Tech Home Inspections



This entry hasn't been re-blogged:

Re-Blogged By Re-Blogged At
Home Improvement
Connecticut Fairfield County Norwalk
New England Professionals
Property Management
Connecticut Professionals
All About Fairfield County, Connecticut.
Investment Property (USA)

Post a Comment
Spam prevention
Spam prevention
Show All Comments
Clint Mckie
Desert Sun Home, commercial Inspections - Carlsbad, NM
Desert Sun Home, Comm. Inspection 1-575-706-5586

Hi David,

I have posted about dryer ducts in the past. Time to revisit the issues with these ducts. Good re post.

Have a great day.

Best, Clint McKie

Jan 04, 2013 10:33 PM #1
Jean Hanley
Coldwell Banker Kivett Teeters - Hemet, CA
Specializing in Folks Who Want To Buy/Sell Homes

Seems like just good old fashioned common sense.  My neighbors had a dryer fire back in August, I believe, and they are still living in their motorhome.  Takes a while to get your life back after a tragedy like this.

Jan 05, 2013 03:31 AM #2
Wallace S. Gibson, CPM
Gibson Management Group, Ltd. - Charlottesville, VA

David * fire safety is a concern for my residents 24/7....fortunately, my HVAC service firm tests smoke alarms and changes batteries twice annually 

Jan 05, 2013 06:09 PM #3
David Popoff
DMK Real Estate - Darien, CT
Realtor®,SRS, Green ~ Fairfield County, Ct

Safety checklists is a must when renting.

Jan 06, 2013 02:58 AM #4
Joe Petrowsky
Mortgage Consultant, Right Trac Financial Group, Inc. NMLS # 2709 - Manchester, CT
Your Mortgage Consultant for Life

I have a deposit on a house that had a fire in the laundry room. Folks should pay attention to your post, as it is an important issue.

Jan 06, 2013 09:12 AM #5
Post a Comment
Spam prevention
Show All Comments

What's the reason you're reporting this blog entry?

Are you sure you want to report this blog entry as spam?


David Popoff

Realtor®,SRS, Green ~ Fairfield County, Ct
Need Help? Ask me a question.
Spam prevention

Additional Information